Skeletal changes of maxillary protraction without rapid maxillary expansion- A comparison of the primary and mixed dentition

Objective: To determine potential differences in treatment efficiencies of face mask therapy without rapid maxillary expansion (RME) at different early dental stages. Materials and Methods: Forty-nine Class III children who were treated with a face mask without RME were divided into two groups according to their pretreatment dental stage. The primary dentition treatment group consisted of 26 subjects and the mixed dentition treatment group consisted of 23 subjects. Lateral cephalograms before treatment (T0), at the end of treatment (T1), and at least 1 year after the end of treatment (T2) were calculated and analyzed. Fourteen cephalometric variables were evaluated by t-test to identify any significant differences in skeletal changes between the two groups during T1-T0, T2-T1, and T2-T0. Results: The primary dentition group showed not only a greater response to maxillary protraction without RME than did the mixed dentition group during T1-T0, but also a greater relapse tendency during T2-T1. As a result, no significant differences were noted between the two groups in the treatment effects of face masks without RME over the time period T2-T0. Conclusion: This study suggests that face mask therapy without RME may be postponed to the early to mid mixed dentition period because the therapy induces similar skeletal changes when initiated at primary or mixed dentition.